1. Field of the Invention
This invention relates generally to a cooling arrangement for an outboard motor, and more particularly to an improved cooling arrangement for discharging coolant that has circulated through an engine of an outboard motor.
2. Description of Related Art
An outboard motor typically includes a housing unit that can be mounted on an associated watercraft and an internal combustion engine disposed above the housing unit. The housing unit carries a propulsion device such as, for example, a propeller to propel the watercraft. The engine powers the propulsion device with a driveshaft and a propulsion shaft extending through the housing unit.
The engine builds heat because air/fuel charges are combusted in the combustion chamber(s) of the engine. Typically, the outboard motor has a cooling system which draws water from a body of water surrounding the outboard motor to the engine and discharges the water to a location out of the outboard motor. The housing unit defines delivery and discharge passages of the cooling system.
In typical arrangements, the discharge passage can extend next to an outer wall of the housing unit. The water that has traveled through the engine flows through the discharge passage. The water, however, can be hot and the outer wall of the housing unit thus can be heated with the hot water. In the meantime, the outboard motor is quite often utilized at sea and salt components, particularly calcium (Ca), can adhere to the outer surface of the wall. Calcium is apt to become white when heated. The outer wall with the whitened calcium detracts from the appearance of the outboard motor.
A need therefore exists for an improved cooling arrangement for an outboard motor that can inhibit the outer wall of a housing unit from becoming white and thereby maintain the good appearance of the outboard motor.
In accordance with one aspect of the present invention, an outboard motor comprises a housing unit adapted to be mounted on an associated watercraft. The housing unit at least in part forms an outer wall exposed outside. An internal combustion engine is disposed above the housing unit. The engine defines a coolant jacket through which engine coolant passes. The housing unit defines first and second coolant passages. The first coolant passage is spaced apart from the outer wall. The first coolant passage communicates with the coolant jacket to allow the engine coolant to flow therethrough. The second coolant passage extends adjacent to the outer wall. The second coolant passage does not communicate with the coolant jacket and allows coolant that has not passed through the coolant jacket to flow therethrough.
In accordance with another aspect of the present invention, an outboard motor comprises a housing unit adapted to be mounted on an associated watercraft. The housing unit at least in part forms an outer wall exposed outside. An internal combustion engine is disposed above the housing unit. The engine defines a water jacket. A cooling system is configured to introduce water from outside of the housing unit to deliver the water to the water jacket and to discharge the water to a location out of the housing unit. The cooling system includes first and second water passages defined within the housing unit. The first water passage communicates with the water jacket. The second water passage does not communicate with the water jacket. The water transfer system delivers a portion of the water to the second water passage upstream of the water jacket. The second water passage extends next to the outer wall. The first water passage is spaced apart from the outer wall by the second water passage.
In accordance with a further aspect of the present invention, an outboard motor comprises a housing unit adapted to be mounted on an associated watercraft. The housing unit at least in part forms an outer wall exposed outside. An internal combustion engine is disposed above the housing unit. The engine defines a coolant jacket. The housing unit defines an internal exhaust passage communicating with an exhaust port of the engine to discharge exhaust gases from the engine to a location out of the housing unit. The exhaust passage is spaced apart from the outer wall. A cooling system is arranged to deliver coolant to the coolant jacket and to discharge the coolant from the coolant jacket. The cooling system includes first and second coolant passages defined within the housing unit. The first coolant passage communicates with the coolant jacket. The second coolant passage does not communicate with the coolant jacket. The cooling system delivers a portion of the coolant to the second coolant passage upstream of the coolant jacket. The second coolant passage extends next to the outer wall. The first coolant passage at least in part is defined in common with the exhaust passage.